Worker-queen conflict and male parentage in bumble bees

Abstract

Male parentage in the bumble bee Bombus melanopygus was estimated using a colour dimorphism as a genetic marker. 1491 males from 17 colonies were classified. 19% of the males originated from the workers while the queens were alive; after their death workers continued to lay eggs, thus in total 39% of the males were worker-produced. The sex ratio of reproductive was male biased (1:6.9, F:M) as well as the investiment ratio (1:2.7). The sex and investment ratios of reproductives produced by the queens were also male biased (1:4.4 and 1:1.7) respectively). There was no significant correlation between the proportion of males produced by the workers while the queens were alive and either colony size or queen lifespan. The queens were, on average, significantly more related to the reproductive brood (r=0.469) than were the workers as a group (r=0.380). The average ‘reproductive success’ (the expected number of alleles identical by descent passed on to the next generation) of the queens was significantly greater than that of the workers. Male production by workers appears to be a manifestation of worker-queen conflict and the workers do not seem to be in ‘control’ in the colonies.